Helena Bonham Carter

Helena Bonham Carter in Harry Potter and the Deathly Hallows: Part 2

Film Deaths

Hamlet (1990) [Ophelia]: Drowned in the river (off-screen); her body is shown afterwards during her funeral procession.

Mary Shelley's Frankenstein (1994) [Elizabeth]: Heart torn out by Robert De Niro in her bedroom. She is later brought back to life when Kenneth Branagh transplants her head onto Trevyn McDowell's body, then dies once again when she commits suicide by setting herself on fire and jumping off of the staircase.
Lemony Snicket's A Series of Unfortunate Events (2004) [Beatrice Baudelaire]:

Tim Burton's Corpse Bride (2005; animated) [Emily, the Corpse Bride]: Killed (exact method unclear) by Richard E. Grant, some time before the story begins (the murder is shown in silhouette during a flashback musical number). She comes back to life when Johnny Depp recites his wedding vows in the woods where she's buried, and eventually returns to the land of the dead, her body transforming into a swarm of butterflies as she does.

Terminator Salvation (2009) [Dr. Serena Kogan]: Dies (off-screen) of cancer, some time between the prologue (set in 2003) and the main story (set in 2018). Her death is mentioned in a newspaper article, and her image is used as an artificial intelligence program later on.

Harry Potter and the Deathly Hallows: Part 2 (2011) [Bellatrix Lestrange]: Explodes and disintegrates when Julie Walters hits her with a magic spell during the final battle.

Dark Shadows (2012) [Dr. Julia Hoffman]: Bitten on the throat by Johnny Depp; her body is shown again afterwards when Johnny and Jackie Earle Haley dump her in the ocean. She later comes back to life as a vampire.

Great Expectations (2012) [Miss Havisham]: Burns to death when a lit candle accidentally falls on the wedding dress she is wearing and the fire spreads; she dies while talking to Jeremy Irvine after Jeremy was able to extinguish the flame.
Alice Through the Looking Glass (2016) [Red Queen]: Turned into a Rust statue, carried by her sister Anne Hathaway , but the White Queen (Hathaway) is turned into rust statue as well holding Red Queen's rust statue. She is restored when the Grand Clock engine and Chronosphere are reconnected.

Merlin (1998 mini-series) [Morgan Le Fey]: Hits her head on a stone step after Miranda Richardson magically causes her to fall; she dies shortly afterwards as Martin Short kneels beside her. (As she dies, her illusion of beauty fades and she resumes her original appearance.) (Thanks to Farzad)

Henry VIII (2003 TV) [Anne Boleyn]: Executed by beheading; her severed head is shown afterwards when the executioner holds it up for the crowd.
The Dark Crystal: She Knows All the Secrets (2019) [All-Maudra] Voicing a character, she is stabbed in the stomach by Benedict Wong.